diff --git a/lighthouse/db/src/stores/beacon_block_store.rs b/lighthouse/db/src/stores/beacon_block_store.rs
index 4ea2882be..84cea2d0d 100644
--- a/lighthouse/db/src/stores/beacon_block_store.rs
+++ b/lighthouse/db/src/stores/beacon_block_store.rs
@@ -96,6 +96,108 @@ mod tests {
     use std::sync::Arc;
     use std::thread;
 
+    #[test]
+    fn test_put_serialized_block() {
+        let db = Arc::new(MemoryDB::open());
+        let store = BeaconBlockStore::new(db.clone());
+
+        let ssz = "some bytes".as_bytes();
+        let hash = &Hash256::from("some hash".as_bytes()).to_vec();
+
+        store.put_serialized_block(hash, ssz).unwrap();
+        assert_eq!(db.get(DB_COLUMN, hash).unwrap().unwrap(), ssz);
+    }
+
+    #[test]
+    fn test_get_serialized_block() {
+        let db = Arc::new(MemoryDB::open());
+        let store = BeaconBlockStore::new(db.clone());
+
+        let ssz = "some bytes".as_bytes();
+        let hash = &Hash256::from("some hash".as_bytes()).to_vec();
+
+        db.put(DB_COLUMN, hash, ssz).unwrap();
+        assert_eq!(store.get_serialized_block(hash).unwrap().unwrap(), ssz);
+    }
+
+    #[test]
+    fn test_get_unknown_serialized_block() {
+        let db = Arc::new(MemoryDB::open());
+        let store = BeaconBlockStore::new(db.clone());
+
+        let ssz = "some bytes".as_bytes();
+        let hash = &Hash256::from("some hash".as_bytes()).to_vec();
+        let other_hash = &Hash256::from("another hash".as_bytes()).to_vec();
+
+        db.put(DB_COLUMN, other_hash, ssz).unwrap();
+        assert_eq!(store.get_serialized_block(hash).unwrap(), None);
+    }
+
+    #[test]
+    fn test_block_exists() {
+        let db = Arc::new(MemoryDB::open());
+        let store = BeaconBlockStore::new(db.clone());
+
+        let ssz = "some bytes".as_bytes();
+        let hash = &Hash256::from("some hash".as_bytes()).to_vec();
+
+        db.put(DB_COLUMN, hash, ssz).unwrap();
+        assert!(store.block_exists(hash).unwrap());
+    }
+
+    #[test]
+    fn test_block_does_not_exist() {
+        let db = Arc::new(MemoryDB::open());
+        let store = BeaconBlockStore::new(db.clone());
+
+        let ssz = "some bytes".as_bytes();
+        let hash = &Hash256::from("some hash".as_bytes()).to_vec();
+        let other_hash = &Hash256::from("another hash".as_bytes()).to_vec();
+
+        db.put(DB_COLUMN, hash, ssz).unwrap();
+        assert!(!store.block_exists(other_hash).unwrap());
+    }
+
+    #[test]
+    fn test_delete_block() {
+        let db = Arc::new(MemoryDB::open());
+        let store = BeaconBlockStore::new(db.clone());
+
+        let ssz = "some bytes".as_bytes();
+        let hash = &Hash256::from("some hash".as_bytes()).to_vec();
+
+        db.put(DB_COLUMN, hash, ssz).unwrap();
+        assert!(db.exists(DB_COLUMN, hash).unwrap());
+
+        store.delete_block(hash).unwrap();
+        assert!(!db.exists(DB_COLUMN, hash).unwrap());
+    }
+
+    #[test]
+    fn test_invalid_block_at_slot() {
+        let db = Arc::new(MemoryDB::open());
+        let store = BeaconBlockStore::new(db.clone());
+
+        let ssz = "definitly not a valid block".as_bytes();
+        let hash = &Hash256::from("some hash".as_bytes()).to_vec();
+
+        db.put(DB_COLUMN, hash, ssz).unwrap();
+        assert_eq!(store.block_at_slot(hash, 42), Err(BeaconBlockAtSlotError::InvalidBeaconBlock));
+    }
+
+    #[test]
+    fn test_unknown_block_at_slot() {
+        let db = Arc::new(MemoryDB::open());
+        let store = BeaconBlockStore::new(db.clone());
+
+        let ssz = "some bytes".as_bytes();
+        let hash = &Hash256::from("some hash".as_bytes()).to_vec();
+        let other_hash = &Hash256::from("another hash".as_bytes()).to_vec();
+
+        db.put(DB_COLUMN, hash, ssz).unwrap();
+        assert_eq!(store.block_at_slot(other_hash, 42), Err(BeaconBlockAtSlotError::UnknownBeaconBlock));
+    }
+
     #[test]
     fn test_block_store_on_memory_db() {
         let db = Arc::new(MemoryDB::open());
@@ -171,7 +273,7 @@ mod tests {
             let mut s = SszStream::new();
             s.append(&block);
             let ssz = s.drain();
-            bs.put_serialized_block(&hashes[i].to_vec(), &ssz).unwrap();
+            db.put(DB_COLUMN, &hashes[i].to_vec(), &ssz).unwrap();
         }
 
         let tuple = bs.block_at_slot(&hashes[4], 5).unwrap().unwrap();
diff --git a/lighthouse/db/src/stores/pow_chain_store.rs b/lighthouse/db/src/stores/pow_chain_store.rs
index 5ded92ad5..aa2b267f7 100644
--- a/lighthouse/db/src/stores/pow_chain_store.rs
+++ b/lighthouse/db/src/stores/pow_chain_store.rs
@@ -23,4 +23,46 @@ impl<T: ClientDB> PoWChainStore<T> {
     }
 }
 
-// TODO: add tests once a memory-db is implemented
+#[cfg(test)]
+mod tests {
+    extern crate types;
+    
+    use super::*;
+    use super::super::super::MemoryDB;
+
+    use self::types::Hash256;
+
+    #[test]
+    fn test_put_block_hash() {
+        let db = Arc::new(MemoryDB::open());
+        let store = PoWChainStore::new(db.clone());
+
+        let hash = &Hash256::from("some hash".as_bytes()).to_vec();
+        store.put_block_hash(hash).unwrap();
+
+        assert!(db.exists(DB_COLUMN, hash).unwrap());
+    }
+
+    #[test]
+    fn test_block_hash_exists() {
+        let db = Arc::new(MemoryDB::open());
+        let store = PoWChainStore::new(db.clone());
+
+        let hash = &Hash256::from("some hash".as_bytes()).to_vec();
+        db.put(DB_COLUMN, hash, &[0]).unwrap();
+
+        assert!(store.block_hash_exists(hash).unwrap());
+    }
+
+    #[test]
+    fn test_block_hash_does_not_exist() {
+        let db = Arc::new(MemoryDB::open());
+        let store = PoWChainStore::new(db.clone());
+
+        let hash = &Hash256::from("some hash".as_bytes()).to_vec();
+        let other_hash = &Hash256::from("another hash".as_bytes()).to_vec();
+        db.put(DB_COLUMN, hash, &[0]).unwrap();
+
+        assert!(!store.block_hash_exists(other_hash).unwrap());
+    }
+}
diff --git a/lighthouse/db/src/stores/validator_store.rs b/lighthouse/db/src/stores/validator_store.rs
index 576fb67db..518d92608 100644
--- a/lighthouse/db/src/stores/validator_store.rs
+++ b/lighthouse/db/src/stores/validator_store.rs
@@ -82,6 +82,91 @@ mod tests {
     use super::super::bls::Keypair;
     use super::*;
 
+    #[test]
+    fn test_prefix_bytes() {
+        let db = Arc::new(MemoryDB::open());
+        let store = ValidatorStore::new(db.clone());
+
+        assert_eq!(store.prefix_bytes(&KeyPrefixes::PublicKey), b"pubkey".to_vec());
+    }
+
+    #[test]
+    fn test_get_db_key_for_index() {
+        let db = Arc::new(MemoryDB::open());
+        let store = ValidatorStore::new(db.clone());
+
+        let mut buf = BytesMut::with_capacity(6 + 8);
+        buf.put(b"pubkey".to_vec());
+        buf.put_u64_be(42);
+        assert_eq!(store.get_db_key_for_index(&KeyPrefixes::PublicKey, 42), buf.take().to_vec())
+    }
+
+    #[test]
+    fn test_put_public_key_by_index() {
+        let db = Arc::new(MemoryDB::open());
+        let store = ValidatorStore::new(db.clone());
+
+        let index = 3;
+        let public_key = Keypair::random().pk;
+
+        store.put_public_key_by_index(index, &public_key).unwrap();
+        let public_key_at_index = db.get(
+            DB_COLUMN,
+            &store.get_db_key_for_index(&KeyPrefixes::PublicKey, index)[..]
+        ).unwrap().unwrap();
+
+        assert_eq!(public_key_at_index, public_key.as_bytes());
+    }
+
+    #[test]
+    fn test_get_public_key_by_index() {
+        let db = Arc::new(MemoryDB::open());
+        let store = ValidatorStore::new(db.clone());
+
+        let index = 4;
+        let public_key = Keypair::random().pk;
+
+        db.put(
+            DB_COLUMN,
+            &store.get_db_key_for_index(&KeyPrefixes::PublicKey, index)[..],
+            &public_key.as_bytes()[..]
+        ).unwrap();
+
+        let public_key_at_index = store.get_public_key_by_index(index).unwrap().unwrap();
+        assert_eq!(public_key_at_index, public_key);
+    }
+
+    #[test]
+    fn test_get_public_key_by_unknown_index() {
+        let db = Arc::new(MemoryDB::open());
+        let store = ValidatorStore::new(db.clone());
+
+        let public_key = Keypair::random().pk;
+
+        db.put(
+            DB_COLUMN,
+            &store.get_db_key_for_index(&KeyPrefixes::PublicKey, 3)[..],
+            &public_key.as_bytes()[..]
+        ).unwrap();
+
+        let public_key_at_index = store.get_public_key_by_index(4).unwrap();
+        assert_eq!(public_key_at_index, None);
+    }
+
+    #[test]
+    fn test_get_invalid_public_key() {
+        let db = Arc::new(MemoryDB::open());
+        let store = ValidatorStore::new(db.clone());
+
+        let key = store.get_db_key_for_index(&KeyPrefixes::PublicKey, 42);
+        db.put(DB_COLUMN, &key[..], "cats".as_bytes()).unwrap();
+
+        assert_eq!(
+            store.get_public_key_by_index(42),
+            Err(ValidatorStoreError::DecodeError)
+        );
+    }
+
     #[test]
     fn test_validator_store_put_get() {
         let db = Arc::new(MemoryDB::open());
@@ -117,18 +202,4 @@ mod tests {
                 .is_none()
         );
     }
-
-    #[test]
-    fn test_validator_store_bad_key() {
-        let db = Arc::new(MemoryDB::open());
-        let store = ValidatorStore::new(db.clone());
-
-        let key = store.get_db_key_for_index(&KeyPrefixes::PublicKey, 42);
-        db.put(DB_COLUMN, &key[..], "cats".as_bytes()).unwrap();
-
-        assert_eq!(
-            store.get_public_key_by_index(42),
-            Err(ValidatorStoreError::DecodeError)
-        );
-    }
 }